Troubleshooting deployment errors in Sharepoint can sometimes be frustrating. Often you get some cryptic error and a inspiring message to "Please try again" when trying again really isn't going to make much of a difference.
Just now I was trying to deploy a site definition after making a minor change to it. I hadn't touched this particular definition in a while, and honestly, I felt a little rusty. I thought I had done the right thing, but when I deployed the solution using STSADM.exe, Sharepoint didn't like my changes.
Now the problem I had is pretty specific but reading through this article you might be able to use some of these troubleshooting steps to find the cause of a similar, or maybe even a not so similar, problem.